Edmonton, Alberta is the farthest north major city in Canada, 587 miles farther north than Minneapolis, which, I hear, gets kind of chilly in winter despite being practically equatorial. And Edmonton is at 2,100 feet altitude, which lowers the temperature another 7 or 8 degrees compared to sea level. The high today in Edmonton was 28 degrees F, or below freezing, in contrast to today's high in, say, Van Nuys of 79 F. So, loyal Edmonton native Colby Cosh is always on the lookout for why frostbite is good for you if it doesn't quite kill you, like it makes your descendants' smarter. He writes in Maclean's:
A new study in the biometric journal Intelligence presents surprising data from Japan that reveal that IQ, imputed from standardized tests given to a large random sample of Japanese 14-year-olds, varies strongly and persistently with latitude. The Japanese are usually thought of—even by themselves—as being quite homogeneous ethnically; the myth of the sturdy, super-cohesive “Yamato race” has not yet been entirely obtruded out of existence. But it turns out that the mean IQs of students in Japanese prefectures apparently vary from north to south by two-thirds of a standard deviation—a spread almost as large as the “race gaps” in cognitive performance which trouble education scholars in multicultural countries like ours. Sun-drenched Okinawans, as a group, do not test as well as the snowbound citizens of Akita.[The Evolutionary Advantages Of A Cold Climate, October 28, 2013]
I don't know anything about Japan so I can't say whether this finding is plausible or not. This pattern isn't necessarily seen in other major Asian countries. In China, the highest achieving region on college tests is said to be the moderately southern province of Fujian, on the coast. In India, southern provinces have come up in the world, with the software capital being Bangalore down south (but also up modestly high, which no doubt helps health and fosters a culture less dragged down by relentless heat and humidity).